The present invention relates to centrifuge rotors, and more particularly to a means to control the location of sample tubes during use.
More particularly, this invention relates to centrifuge rotors of the kind described in GB Patent Specification 2 233 584B. The invention is concerned with providing improvements to the device of the said GB Patent which enable higher speeds, and more consistent performance to be achieved. It is also desirable if when using a transparent rotor, performance of the centrifuging of the sample tubes is readily monitored by a strobing means.
One problem with the previously described centrifuge rotor was that the degree to which the sample tubes swung out during rotation was variable, and moreover there was the variability of flexure around the disc carrier which therefore gave inconsistent performance. The present invention aims to solve these problems and to provide a higher speed of operation.
Another problem with the previously described centrifuge rotor was the effectiveness of the seal.
According to a first aspect of the present invention there is provided a centrifuge rotor including a sample carrier enclosed within an outer housing and being rotatable about a principal axis of rotation of the rotor, the sample carrier having a peripheral zone for holding sample tubes in an orientation parallel to the said axis when at rest and the sample carrier being capable of deflecting to enable sample tubes to swing out under the effect of centrifugal force, wherein the sample carrier incorporates petal-like carriers for each tube equally spaced around said sample carrier, and characterized in that the central region of the sample carrier is of a thicker material than that of material forming said petal-like carriers, so that any flexing is concentrated in the region of said petal-like characters.
According to a second aspect of the present invention, there is provided a centrifuge rotor which comprises a sample carrier rotatable about a principal axis of rotation of the rotor, the sample carrier having a peripheral zone for holding sample tubes to permit centrifuging, and an outer casing having two parts and enclosing the sample carrier, the two parts of the outer casing being sealed together at a peripheral zone by sealing means which is arranged so that sealing is increased by the effect of the centrifugal force arising during centrifuging.
Preferably, the sealing means is a sealing ring having a profile in the form of a V-shape whose vertex is directed outwards. The limbs of the V then flex outwards during the centrifugal force and seal to the two parts in an effective manner.
According to another aspect of the present invention there is provided a centrifuge rotor, including a sample carrier enclosed within an outer casing and being rotatable about a principal axis of rotation of the rotor, the sample carrier having a peripheral zone for holding sample tubes in an orientation parallel to the said axis when at rest, and the sample carrier being capable of deflecting to enable sample tubes to swing out under the effect of centrifugal force, said centrifuge rotor being arranged so that beyond a given speed of rotation of the sample carrier, deflection of the tubes is constrained to a predetermined angle.
In practice, for example, a rotor may have an operational speed in the region of about 12,000 rpm and the deflection would be constrained at speeds above about 6 to 6,500 rpm. Thus, from start up the tubes progressively swing out and become constrained from about half operational speed and upwards as the rotor builds up in speed to its operational level.
Suitably the predetermined angle to which the tubes are constrained may be in the region of 40xc2x0 to 45xc2x0. Constraint may be achieved by arranging for the tube to deflect to a point where it touches and is thereby constrained by the outer casing of the centrifuge; or an alternative means of achieving this constraint is by use of a sample carrier having a peripheral end region which constrains movement of the sample tubes.
Thus, conveniently the centrifuge rotor is enclosed within a transparent outer casing and strobing means can be provided for examination of samples when being centrifuged.
It is preferable for the sample carrier to incorporate apertured, petal-like carriers for each tube equally spaced around said sample carrier and integrally connected to a central region of the carrier which is of a thicker material than that of material forming said petal-like carriers, so that any flexing of the sample carrier during centrifuging is concentrated in the region of said petal-like carriers. This arrangement enables the petal-carriers to each flex independently to a controlled angle without significantly affecting the rest of the carrier. Each petal-like carrier can be joined to the central region of the carrier along a line of weakness which enables each petal-carrier to flex about said line of weakness as the tube swings outwards under the effect of the centrifugal force.
The term petal-like carrier is used here to refer to a carrier of thin material which behaves like a petal or leaf opening out and closing relative to the central region.
Preferably the centrifuge rotor should be enclosed within an outer casing which can be opened and which when closed and during the rotation of centrifuging maintains an effective seal.
Thus the centrifuge rotor may include an outer casing of essentially two parts enclosing the sample carrier, the two-part outer casing being sealed together at a peripheral zone by sealing means which is arranged so that sealing is increased by the effect of the centrifugal force arising during centrifuging.
Preferably the sealing means is a sealing ring having a profile in the form of a V-shape whose vertex is directed outwards. The limbs of the V then flex outwards during the centrifugal force and seal to the two parts in an effective manner.